Highly strained In0.28Ga0.72As1-xNx/GaAs single quantum well (SQW) structures grown by molecular beam epitaxy for different N mole fractions have been investigated by photoreflectance (PR) spectroscopy at room temperature. The influence of nitrogen on the electronic structure and on the optical properties of the quantum well has been analysed. The observation of excited state transitions allowed demonstrating a type I band line-up for both heavy and light holes, for such indium and nitrogen mole fractions. All the observed optical transitions have been identified on the base of the results of the envelope function calculation including strain effects. The dependence of the optical transitions on the nitrogen content has been derived and compared with the experiment.